Jet engine structure



Jan. 26, 1965 H. v. WHITE JET ENGINE STRUCTURE 5 Sheets-Sheet 1 FiledApril 4, 1962 INVENTOR. way/v u IVA I75 Jan. 26, 1965 H. v. WHITE JETENGINE STRUCTURE Filed April 4, 1962 3 Sheets-Sheet 2 INVENTOR. #4844 1WW??? A a/w? G W Jan. 26, 1965 H. v. WHITE 3,166,903

JET ENGINE STRUCTURE Filed April 4, 1962 3 Sheets-Sheet 3 I a) J E[AVG/IVE! INVENTOR. #934 ill 1/ 11 17/725 WC W United States PatentOfiice WW3 Patented Jan. 26, 1965 3 166 9% extending supporting membersor struts, one of which is I indicated generally at 12. The strut may beintegral Hay, V- gg; ig fgiii i %t i g t9 @emml with the outer casing,or it may be welded thereto, and Eie fi i {:ampany 8 68320535651 M Newmay also include stiifeners in the form of channels or Filed Apr. 4,1%2, Ser. No. 185,773 rings 1414 located at the outer end of the strut.The l Claim. 6-39.31) strut preferably is provided with a heat shield orbaffie 16 attached, by suitable means, at 18, 19, 20 and 21 to the Thisinvention relates to jet engine structure and, more outer casing and thecentral portion of the strut. Genspecifically, to a lightweight, loadbearing frame structure erally conical, lightweight, sheet-metalcomponents 22 and for use in an axial-flow jet engine including improved24 are also provided which, when welded or otherwise means forconverting distributed loads to concentrated permanently attached to theheat shield, form an annular loads. opening for the hot exhaust gas jet.Adapted to be It has become increasingly important in the design oflocated at the inner end 26 of the strut is a bearing (not jet engines,particularly gas turbine engines for aircraft, shown) for the turbinerotor, th bearing being u t d to provide engines which are light inweight. However, in a kno n manner fro th i l member 23 Th when enginecomponents are made from thin-walled, struct 12 is preferably hollow,being fabricated from sheet-metal materials, particularly the structuralor frame lightweight sheet-metal or, as shown, comprising alightcomponents, unwanted stress concentrations may be inweight casting.Bisecting the strut is a substantially cytroduced. For example, it issometimes desirable to conlindrical member indicated generally at 30,which extends trol the velocity of the exhaust gas stream issuing fromslightly forward of the strut 12, at 32, and aft thereof, the tailpipeof an axial-flow jet engine by means of a at 34-. While hereinafterreferred to as a cylinder, it variable-area nozzle. One known type ofnozzle for Such will become apparent that pursuant to the teachings ofan engine utilizes a centrally-located plug. The plug, my invention thesupport member 3t is not, in fact, a being axisymmetric, may besupported by a cylindrical perfectly circular cylinder. In theembodiment shown, member integrated in some manner with the main enginethe cylindrical member 39 is attached at 36 to a support structuralcomponents or frames. One problem that member 38 for a plug 4% actedupon by the exhaust arises is how to efficiently transition the loadswhich are gases issuing from the engine. As seen in the drawings,imposed on the axially-extending plug by the gas stream the plug is acontinuation of the inner flow defining wall to the radially-extendingframe members. In other Words, member 2%, being attached thereto at 41.Internal reinwhat may be described as an essentially uniform, diS- 3Oforcing members 42 and 44 are provided to maintain tributed axial loadin the cylindrical member must be rigidity in the structure. Inaddition, a reinforcing ring transformed into a shear load. Also, andwhat is more 46 is provided adjacent the downstream edge of thecydifiicult, where a plurality of radially-extending frame lindricalmember 34 for a purpose hereafter described members or struts are used,the distributed axial load must in more detail. be transmitted asdistributed shear into the strut walls, To better describe theinvention, use has been made which necessarily results in concentratedaxial loads in of schematic type drawings. FIGURE 2 illustrates the thecylindrical member. substantially cylindrical member 39 as if rolled outinto Accordingly, the primary object of the present invena plane.Accordingly, the struts 12 are depicted as intertion is to provide animproved load distributing frame secting the plane at right anglesthereto. As stated above,

structure for use in a lightweight axial-flow jet engine. the presentinvention has to do with the means by which In the described embodiment,the invention comprises the substantially uniform or distributed axialload, intromeans for taking a distributed, essentially uniform axialduced in the cylindrical member 3% by forces acting on load in asubstantially cylindrical support member and the plug and supportingstructure, is transmitted to the transmitting the load into a pluralityof radially-extending struts 12 as concentrated axial, i.e., distributedshear loads. struts intersecting the member, at the same time avoidingAssuming gas flow to be in the direction of the arrow in curved loadpaths. FIGURE 2, at the first instant that the load is applied,

Although the invention is particularly pointed out and i.e., exhaust gasflow occurs, most, if not all, of the load distinctly claimed at the endof the following detailed will be applied to the downstream tip 50 ofthe strut, or description, the invention will perhaps be better under-50 where the strut intersects the cylindrical load bearing stood andother objects and advantages become more member 3% This is so since,obviously, the shortest disreadily apparent when the description is readin conjunctance between a point on the strut-to-cylinder intersectiontion with the following drawings in which: line and a reference area(ring 46) downstream in the FIGURE 1 is a side view, partially in crosssection, of plane 30 is represented by line a in the plane. Stress alightweight frame member in an axial-flow jet engine will thus beconcentrated in the cylinder and would recmbodying the invention; andmain concentrated far downstream of the strut tip in the FIGURES 2, 3and 4 are schematic drawings illusconventional construction. However,the invention elimitrating the manner in which the invention enablesloads nates this unwanted stress concentration and does so in to be moreefiiciently transmitted from a cylindrical supa comparatively shortaxial distance, the latter feature port member to a plurality ofradial-extending frame being especially desirable in the construction oflarge members. diameter, lightweight engines.

Turning now more specifically to the drawings, FIG- To explain, assumethat in addition to distance a, an URE 1 is a sectional view of a framemember, e.g., a infinite number of distances, or elements, are laid outrear turbine frame in an axial-flow jet engine utilizing the in theplane, i.e., in the cylinder 34 These elements invention. It will beunderstood that while the rear turmay be represented by straight lines bthrough h and b bine frame is shown for purposes of illustration, thethrough h, on either side of element a, which connect invention is notlimited to this portion of the engine and the struto-cylinderintersection with a reference line may find equal application elsewhere.In the drawing, (ring 4-6) in the plane 30. In other words, thesesonumeral 10 is an outer casing or shell which forms a duct calledstraight line elements may be visualized as an for the main jet exhaustflow indicated by the large arrows. m infinite number of stringsstretched between two points, The flow comes from the turbine section(not shown) one point being on the strut wall approximately half-waywhich is located upstream of a plurality of radiallybetween the ends ofthe strut, and the other point being on the cylindrical member in thevicinity of the circumferential stilifening ring id. in the schematic ofPEG- URE 2 the above-described arrangement has the appearance of anumber of triangular shaped areas fanning out from the strut and comingtogether adajacent the stiillener ring. The straight line elements inthese areas act to equalize load distribution by equalizing thestillness of the load paths, i.e., these paths are now straight, ratherthan curved, extending from an infinite number of zones along the strutperiphery to the desired zone of the cylindrical support member 30.

The concept may perhaps be more clearly understood if resort is made tothe device of passing an imaginary plane through one of thestraight-line elements, e.g., h,

V the plane containing element 11 of the cylinder structure (Wall) andbeing pierced by the engine ccnterline. Such a plane ABCD is shown inFIGURE 3. From the draw ing it will be clear that without element h, theintersection of the plane and. the cylinder structure would be thecurved (dotted) line. However, when the construction disclosed by theinvention is utilized, the cylinder wall at the point of intersectiontakes the form of the straight line it between the points (x) and (y) onthe strut and at the location or" stiffening ring 46, respectively.Obviously, if a tensile load were then applied at point (y), i.e., tothe ring 46, this load would be immediately applied to point (x),whereas if element It were not provided, that is, if the part of thewall of member 3% in the plane ABCD were, in fact, cylindrical (curved)rather than the straight line element, as herein defined, the curvedload path in the cylinder wall (dotted line in FIG. 3) would first tendto flatten out before tension could be transmitted to point (x). Thus,throughout the infinite number of straight line elements, represented inFIGURE 2 by lines b4: and b'h, and a, representing the traces of afamily of planes passed through the wall of member 30 the axial loads atthe stiffener ring are immediately and uniformly distributed along thest ut-tocylinder connections.

In actual practice, the described arrangement results in a cylinderconfiguration perhaps best illustrated with the help of FIGURE 4. Assumea series of planes E-E, FF, G-G, as shown in FIGURE 2, passed throughthe cylinder 39 and perpendicular to the engine axis. In FIGURE 4, thedotted lines represent the original diameter of the cylinder, i.e., thediameter that exists at the ring 46 and adjacent the baffle connectionat Ztl, in FIG URE 1. Consider first, plane F-F. Each portion of theactual wall indicated at P will be curving inwardly towards the engineaxis, the curve being of a continually changing radius moving outwardlyfrom the strut centerline. Intermediate the two continually changingportions is a central portion F" which represents the portion of thesupport member 3%) between the adjacent areas containing the straighdincelements. In contrast to portions F, these central portions F" do have aradius which is unique for each point through which is passed a planeperpendicular to the engine axis (such as plane F-F), this radius beingconcentric to the engine axis. Thus, it will be clear that at some pointalong the wall of the substantially cylindrical member 30 between theconnection at 20 and the ring 46 a low point, or smallest concentricradius will exist and that on both sides of these intermediatecylindrical portions there exist portions of the cylinder ofcontinuously changing curvature extending on out to the strutperipheries. Similarly, the planes EE and GG will delineate portions ofthe actual structure (wall) of support member 3% (E' and E", and G andG) which will be either of continually changing radii or of a singleradius concentric to the original cylinder radius.

The lateral and longitudinal extent of each of the continuously curvingareas of straight line elements, as viewed in FIGURES 2 and 4, willdepend, respectively,

l on (1) the number, spacing, and thickness of the struts l2, and (2)the axial length or" each strut and the axial distance in which it isdesired to accomplish the load er 'ualization (in this case, thedistance indicated at 34 in FlGURE l), i.e., the transmitting of thedistributed axial loads to distributed shear loads at each strut.

It should be realized that a completely uniform load distribution at thearea of the ring 46 is not possible for several reasons. For example,the walls of the struts 12 will not be of completely uniform stillnessso that some straight line elements may pull more than others. Also, thering 46 will have some radial and circumferential loads induced on itdue to the angle of approach of the straight line elements, which causesome deflection that will further militate against complete uniformityof distribution of the axial loads. Nevertheless, it has been found thatby utilizing the invention, less than 20% deviation from the uniform, atthe ring, may be achieved.

The above-described arrangement will therefore be seen to differ fromthe conventional jet engine frame construction which typically hasrequired one or more of the following: (I) long (axial) sections to takeout the loads, with or without thickness variation in the cylinder wallitself, (2) the addition of very heavy rings at the leading and trailingedges of the struts, (3) use or a multiplicity of circumferential ringsin the transition zone (cg, zone 34 in FZGURE l), and (4) longeronsextending tar downstream of the struts.

While perhaps best suited for structures within the induced side loads,i.e., loads acting perpendicular to the engine axis, are not excessive,with the addition of small, lightweight, sheet-metal channels in theplane of the struts, the above-described invention will provide alighter structure than heretofore known and, moreover, an improvedarrangement for transmitting uniformly distributed axial loads to aframe as distributed shear (concentrated axial) loads.

While I have described my invention as being useful in the embodimentshown, it should be understood that it will have application in otherstructures where loads are present and therefore the claim which followsshould not be taken as being limited thereto.

What I claim is:

In a fluid flow engine a lightweight supporting structure including aframe, said frame having:

inner and outer motive fluid flow-defining wall portions;

a plurality of circumferentially-arranged, radially extending strutsjoining said inner and outer wall portions and providing supportthereto;

a substantially cylindrical sheet metal support member located generallywithin said inner wall portion, said support member being intersected bysaid struts adjacent one end of said support member;

and a fiow guiding member connected to said support member at the otherend thereof, said motive fluid acting on said tiow guiding member so asto impose a substantially uniformly distributed axial load about saidother end of said substantially cylindrical support member;

said support member having a plurality of discrete, generallytriangular-shaped, wall portions, said triangular-shaped wall portionsextending longitudinally of the support member from the upstreamextremity of the strut to said other end of said support member, andlaterally of the strut along the support member from a minimum distanceat said upstream strut extremity to a maximum distance at the other endof said support member so that the bases of said triangular-shaped wallportions join at said other end,

each of said triangular-shaped wall portions being comprised of thetraces of a family of skewed planes passing through said support memberwall, each plane being intersected by the axis of said support 5 6member but not containing said axis with the exceptransmit said load tosaid struts with the avoidance tion of a single plane central to each ofsaid wall of curved load paths in said support member. portions locatedat the downstream extremity of said strut, References Cited in the fileof this patent said traces representing straight line elements of said 5UNITED STATES PATENTS support member wall extending from the strutintersection therewith to said other end of said mem- 3O5O937 James eta1 1962 ber, said elements substantially uniformly reacting FOREIGNPATENTS to Said distributed axial load in a manner such as to 1 07 73Germany Man 31 19 0

